Speaker
Description
Standard quantum mechanics does not allow for systems existing in quantum superpositions of different times, since time is not an observable but a parameter. For the same reason the standard formalism does not allow for entanglement of states taken in different times. In this context I want to recall an atomic-interferometry experiment which is not widely known, but which may be regarded as the case where a superposition of different times was actually observed. Secondly, I will outline a formalism where one distinguishes between a four-position observable (with x_0=ct included) and a flowing time parameter tau. The dynamics is given by a flowing-time Schroedinger equation and spatial expansion of the Universe is the process that compensates localization of the Universe wave function around a given moment of the flowing time. Superpositions and entanglement of different four-positions are in this formalism possible. If time allows, I will say a few words about a looped quantum dynamics, with loops in space and time.
